In the prior art, there exist many examples of collection of agents from the air for bioassay. For example, the following publications describe various methods of allergen, pathogen and toxin collection for assay: Yao et al (2009) in Aerosol Science volume 40, pages 492-502;    Noss et al (2008) in Applied and Environmental Microbiology, volume 74, pages 5621-5627;    King et al (2007) in Journal of Allergy and Clinical Immunology, volume 120, pages 1126-31;    Earle et al (2007) in Journal of Allergy and Clinical Immunology, volume 119, pages 428-433;    Peters et al (2007) in Journal of Urban Health: Bulletin of the New York Academy of Medicine, volume 84, pages 185-197;    Yao and Mainelis (2006) in Journal of Aerosol Science, volume 37, pages 513-527;    Platts-Mills et al (2005) in Journal of Allergy and Clinical Immunology, volume 116, pages 384-389;    Sercombe et al (2004) in Allergy, volume 60, pages 515-520;    Custis et al (2003) in Clinical and Experimental Allergy, volume 33, pages 986-991;    Polzius et al (2002) in Allergy, volume 57, pages 143-145;    Tsay et al (2002) in Clinical and Experimental Allergy, volume 32, pages 1596-1601;    Parvaneh et al (2000) in Allergy, volume 55, pages 1148-1154; and    McNerney et al (2010) in BMC Infectious Diseases, volume 10, pages 161-166 and device in U.S. Pat. No. 7,384,793.
Other known methods of sample collection include trapping of volatile organic compounds (VOC) on activated carbon, de-sorption and analysis by mass spectrometry. See Phillips at al (2010) in Tuberculosis, volume 90, pages 145-151 and references therein. VOC's are not considered encompassed by the present invention since the assays are strictly chemical in nature, and are not bio-specific as defined here. By bio-specific assays is meant assays wherein the result is determined by a biological specificity such as nucleic acid specificity, antibody specificity, receptor-ligand specificity and the like. While diagnostic specificity may be achieved by VOC analysis, this is inferred by presence and amount of groups of defined organic compounds.
The foregoing prior art publications describe “dry” methods using pumping and filtration, wiping, passive deposition, electrokinetic transport etc; usually followed by an extraction step and application of the extract to an assay.
Methods for collection in a liquid stream have been described in the patent literature including Yuan and Lin in US Patent Application 2008/0047429A1, and Bashi at al. in U.S. Pat. No. 6,484,594. While efficiently collecting agents from the air, such liquid streaming systems inevitably result in high dilution of the sample. There is a consequent trade-off in sensitivity unless the agents are re-concentrated.
Northrup et al. in U.S. Pat. Nos. 7,705,739 and 7,633,606 describe an autonomously running system for air sampling and determination of airborne substances therein. They do not specify the exact method of air sampling, nor detail how it is transferred to an assay system.
There exist numerous commercially available systems for air purification based on filtration or electrostatic precipitation. For a general description see the Environmental Protection Agency article “Guide to Air Cleaners in the Home”, U.S. EPA/OAR/ORIA/Indoor Environments Division (MC-6609J) EPA 402-F-08-004, May 2008. Numerous commercial examples of systems exist using either High Efficiency Particulate Air (HEPA) filters or electrostatic precipitation filters. Such systems are widely used for removal of particulate matter or allergens from air, including as part of domestic heating, ventilation and air conditioning (HVAC) systems. HEPA filters have the advantage of removal of particles down to the micron size range, whereas electrostatic precipitation methods have the advantage of entailing high volume flow with little or no pressure differential. See US patent by Bourgeois, U.S. Pat. No. 3,191,362 as a detailed example for the technical specification of an electrostatic precipitation system. While efficiently removing agents from the air, such air purification systems do not lend themselves to collection of samples for analysis.
Electrokinetic-based air cleaning systems have been developed and formerly commercialized by the company Sharper image under the trade name Ionic Breeze. The original electrokinetic principle was enunciated by Brown in U.S. Pat. No. 2,949,550. This was further improved by Lee in U.S. Pat. No. 4,789,801 for improving airflow and minimizing ozone generation. Further improvements for the commercially available system are described in US patents by Taylor and Lee, U.S. Pat. No. 6,958,134; Reeves et al, U.S. Pat. No. 7,056,370; Botvinnik, U.S. Pat. No. 7,077,890; Lau et al, U.S. Pat. No. 7,097,695; Taylor et al, U.S. Pat. No. 7,311,762. In the foregoing descriptions of devices using electrokinetic propulsion, a common element is a high voltage electrode consisting of a wire. A very steep voltage gradient is generated orthogonally to the wire because of the very small cross-sectional area of the wire. The high voltage gradient causes the creation of a plasma consisting of charged particles, and kinetic energy is imparted to the charged particles by the high voltage gradient. The resulting net air flow is created by exchange of kinetic energy between charged and uncharged particles, and the net air flow is directed by the juxtaposition of planar electrodes which are at zero or opposite sign voltage to that of the wire electrode. Charged particles are electrostatically precipitated on to the planar electrodes which may periodically be removed for cleaning. This body of work is directed toward air purification not sample collection. However, as first described by Custis et al. (2003), the Ionic Breeze device has been adapted for sample collection for allergen analysis by wiping down the electrodes with a paper tissue. The allergens were extracted from the tissue and subject to an immuno-assay. The Ionic Breeze was also used in the works of Peters et al. (2007) and Platts-Mills et al. (2005) for allergen collection for immunoassay analysis. Earlier, Parvaneh et al. (2000) described an ionizer device with a “metal cup having a conductive surface as a collector plate”, from which allergens are extracted for assay. It is not evident how the sample is collected on the inside of a metal cup and does not adhere to the entire surface. The device was made by Airpoint AB, Stockholm, Sweden. However, there is no public information concerning the manufacture or sale of such a product by Airpoint AB, there is insufficient information for one skilled in the art to be able to understand the details of the device, and no similar device was used by the same authors in subsequent publications on environmental allergen detection. There is no mention of focusing of the sample into a potential well created by a voltage gradient.
Yao et al (2009) and Yao and Mainelis (2006) have described methods for collection of bio-assayable agents on to an assay means or device. Yao and Manielis (2006) describe blocks of agar gel in electrical contact with planar electrodes, and Yao et al (2009) describe a microtiter plate interposed between planar electrodes. Both of these works describe a flow of air driven by a pump, and electrostatically precipitating the agents to be analyzed on to the assay means. The electrodes and the agar blocks have substantially the same area in these works.
McNerney et al (2010) describe a breathalyzer device, where the individual breathes or coughs into a breathing tube, the sample collects on the internal surface of a tube, is scraped with a plunger on to an optical biosensor, an immunological binding reaction is performed and the biosensor utilizes an evanescent wave illumination system to determine the presence or absence of M. tuberculosis by scattered light.
None of the above methods consider the use of an electric field gradient forming a potential well to focus the agents on to a collection means for an assay device.
A vast number of assay methods for immunoassays and nucleic acid hybridization assays are well-known in the art, of varying complexity, of which there are too many to review here. The large majority require some label to achieve a detectable signal. The label may be radioactive, fluorescent, enzyme with chromogenic substrate, enzyme with electro-active product to produce an electrical signal. Such methods have revolutionized assay procedures, but require inconvenient interception with protocol steps for washing and removing unbound agents and unbound label. More appropriate are self-performing or dip-stick assays. Lateral flow self-performing assays still require a label, usually dried within the device, which then reveals a positive result when the label is bound at a specific site on the lateral flow strip, and appears as the localized concentration exceeds the concentration of the flowing unbound label Lateral flow assays are reviewed comprehensively by Gordon and Michel, see 1, below. Further assays are known which require no label and use the modification of the optical properties of a binding surface, see refs 2-10 below.    1. Gordon J, Michel Analytical sensitivity limits for lateral flow immunoassays. Clinical Chemistry. 2008; 54(7):1250-1.    2. Brecht A, Ingenhoff J, Gauglitz G. DIRECT MONITORING OF ANTIGEN-ANTIBODY INTERACTIONS BY SPECTRAL INTERFEROMETRY. Sensors and Actuators B-Chemical. 1992; 6(1-3):96-100.    3. Gauglitz G, Brecht A, Kraus G, Nahm W. Chemical and Biochemical Sensors Based on Interferometry at Thin (Multi-)Layers. Sensors and Actuators B-Chemical, 1993; 11(1-3):21-7.    4. Cunningham B, Li P, Lin B, Pepper J. Colorimetric resonant reflection as a direct biochemical assay technique. Sensors and Actuators B-Chemical. 2002; 81(2-3):316-28.    5. Petrou P S, Ricklin D, Zavali M, Raptis I, Kakabakos S E, Misiakos K, et al. Real-time label-free detection of complement activation products in human serum by white light reflectance spectroscopy. Biosensors and Bioelectronics. 2009; 24(11):3359-64.    6. Concepcion J, Witte K, Wartchow C, Choo S, Yao D F, Persson H, et al. Label-Free Detection of Biomolecular Interactions Using BioLayer Interferometry for Kinetic Characterization. Combinatorial Chemistry & High Throughput Screening 2009; 12(8):791-800.    7. Zavali M, Petrou P S, Goustouridis D, Raptis I, Misiakos K, Kakabakos S E. A regenerable flow-through affinity sensor for label-free detection of proteins and DNA. Journal of Chromatography B. 2010; 878(2):237-42.    8. Zavali M, Petrou P S, Kakabakos S E, Kitsara M, Raptis I, Beltsios K, et al. Label-free kinetic study of biomolecular interactions by white light reflectance spectroscopy. Micro & Nano Letters. 2006; 1(2):94.    9. Abdiche Y, Malashock D, Pinkerton A, Pons J. Determining kinetics and affinities of protein interactions using a parallel real-time label-free biosensor, the Octet. Analytical Biochemistry. 2008; 377(2):209-17.    10. Abdiche Y N, Malashock D S, Pinkerton A, Pons J. Exploring blocking assays using Octet, ProteOn, and Biacore biosensors. Analytical Biochemistry. 2009; 386(2): 172-80.
Further US patents by Chen (U.S. Pat. No. 5,804,453) and Tan at al. (U.S. Pat. No. 7,656,536) describe label free methods utilizing fiber optics. A recent application of label-free direct binding technology is the Octet system of Fortebio (Pall ForteBio Corp, Menlo Park, Calif.). The Octet system is designed for immersing eight analyte-specific biosensor probes based on fiber optics into separate wells of a micro-well plate and directly observing binding of the analyte molecules from the wavelength shift produced by interference between incoming and reflected light, by means of a spectrophotometer. This is thus a true dipstick assay method.
Thus, while many of the above elements are known or commercially available, there is a need for a simple portable integrated system. Such a system could be used by consumers or public health practitioners for determining the presence of allergens or pathogens in buildings. Such a system could easily be deployed in public environments for the monitoring and early recognition of pandemics, such as influenza pandemics. Such a system could be deployed at international transit points and points of entry for early recognition of bioterrorism agents. Such a system could be used by military personnel in the field for early detection of biowarfare agents.
The present invention is directed to improvements over the systems and methods noted above.